The invention relates to electronic calculators, specifically to a portable, hand-held calculator, and more particularly to a student calculator which includes a new feature useful in the teaching of mathematics.
Small portable calculators are commonly used in the mathematics classroom today. In many mathematics classes in high schools and elementary schools, each student in a class uses a student calculator and is taught various mathematical functions and manipulations by a teacher using a calculator having similar functions. U.S. Pat. No. 4,154,007 introduced the overhead projectible calculator, with a transparent liquid crystal display for projection onto a screen. Using such a projectible calculator with keyboard layout similar to the students' calculators, the mathematics teacher can show the solving of mathematical problems while instructing students in the classroom. Further refinements have been developed with U.S. Pat. Nos. 4,836,786 and 5,035,502, wherein not only the LCD of the calculator but also the keyboard is transparent and projectible. Thus, the students see not only the LCD as projected, but also the instructor's entries onto the keyboard.
Such projectible calculators have made great progress in furthering the use of electronic calculators in the teaching of mathematics. However, in the field of classroom calculators there has been a need for an effective teaching tool which can be used to direct students in learning alternative mathematical manipulations to achieve a given result, helping to teach factoring and the associative and distributive properties in mathematics. This is the purpose of the present invention described below.